Final Report

FINAL REPORT Rob Rock and Andy Crawford Building and Evaluating a Pedal Powered Prone Workstation and Row Crop Cultivation Tool SARE FNE-07-603 Thanks Rob Rock and Andrew Crawford would like to thank SARE Northeast for large portions of the funding for this project, Ron Hernandez of Stray Cat Farm for generous use of his welding equipment, Arethusa Collective Farm for the beds used thus far in the trials, the staff of the Old Spokes Home for a wealth of ideas and a free used bicycle part here and there, and all of the Burlington Intervale farms for their encouragement, interest, and patience while we were building the prototype in and around the farmer barn. We would also like to thank Pine Street Studios LLC, who made it easy for us to continue building vehicles and show our work on these projects after all the original trials were completed for the SARE grant. Andrew B. Crawford Robert E. Rock 14 Decatur St. A 77 Intervale Ave. Burlington VT 05401 Burlington VT 05401 (802)324-1915 (802)233-5464 [email protected] [email protected] [email protected] Goals The goal of our project was to assess the viability of using human/bicycle powered vehicles to accomplish a number of tasks found in a vegetable row-cropping system. During the 2007 and 2008 growing seasons, with the use of personal and SARE funds, we designed, built, and tested what we have descriptively called a ªtwo person pedal powered prone workstationº. Sets of trials were conducted for the tasks of hand weeding and transplanting. The vehicle©s suitability for mechanical cultivation with one and two riders was also tested, and some strategies for using the vehicle for cultivation were developed. For our fourteen hand-weeding trials, we saw an average 28% decrease in the time spent per bedfoot hand-weeding a 3 row closely planted crop. This was equivalent to an average time savings of 19 minutes and 42 seconds +/- 1 second on a 400 foot bed. The nine transplanting trials resulted in an average 9.22% +/- 0.16% decrease in total planting time with the prone workstation. The number of samples in the transplanting trial is not significant enough to verify that this margin is statistically robust, but is consistent enough to give users an indication of what can be expected. Over a 400 foot bed the actual difference in time amounts to 7 min. 28.8 seconds +/- 7.8 seconds. During cultivation experiments, we found that any task requiring more than approximately 0.45 kN of draft force was physically unsustainable by two healthy and fit adults. A drag style spike tooth harrow was the most aggressive cultivation tool successfully pulled. The estimated total human muscle power output to achieve this is on the order of 500 +/- 100 Watts, or 0.67 +/- 0.13 HP, which puts a reasonable upper limit on the cultivation tasks that can be attempted with two riders on this vehicle and other similar human powered vehicles. Human power output below that value is sufficient to lightly cultivate the un-cropped portions of a 48 inch wide bed with tools intended for hand and wheelhoe use. Farm Profile The project was a collaboration between Andrew Crawford and Rob Rock, two organic vegetable farmers working for Arethusa Collective Farm located on the Intervale in Burlington, Vermont. The farm cultivates roughly 14 acres, growing a variety of market garden crops for the Saturday Farmer's Market in Burlington, but realizes the greater part of its revenue from the wholesale of mesclun mix, carrots, eggplants, and hoop house tomatoes to area natural food stores, co-ops, restaurants, and grocers. The predominant soils on the farm consist of sandy loam on river bottom land, and are comparatively light and easy to work, with no hills in the fields present. Participants Our technical advisor, Dr. Daniel Baker, UVM Assistant Professor of Community Development and Applied Economics, offered us guidance in the planning and the development of a timeline for the term of the grant process, as well as guidelines for data collection procedures. Project Activities 1.) Vehicle Design and Design Assessment The prone workstation is a quadracycle, or four wheeled pedal powered vehicle. The design positions two people side-by-side, who would ordinarily be crawling on their hands and knees down a bed of crops. The vehicle roughly resembles a massage table with forehead and chin rests, so that the riders are looking directly at the ground ahead of them. Each rider has their feet on a set of bicycle pedals, and turns a crank which transmits power to a rear wheel, one for each rider. In this position, all of the crop rows in the bed are within reach, the head and back are rested in a comfortable position, and both hands are free to work. We did have a little help (and inspiration) from a book written by a very funny and eccentric bike builder calling himself the ªAtomic Zombieº. Some of the basic concepts for our machine's transmission were roughly adapted from one of his designs, but perhaps more importantly we were really encouraged because he builds out of scrap metal and junked bikes in a very primitive welding shop. Some of his tutorials may be found at http://www.atomiczombie.com. We used only the most basic metal working tools, and the skills required for the project could be easily obtained from a night class at an area vocational school, with the help of a little bit of practice. A similar vehicle could be built using a moderate to large sized drill press, an angle grinder, a sturdy vise, a 220V arc (or ªstickº) welder, as well as a few of the basic hand tools of the metal shop such as a tap and die set and files. We originally had planned to have some parts machined, but due to delays at the machine shop, we eventually went ahead and made our own parts from existing used bicycle components. The design phase was fairly easy compared to the construction. It was probably late in August once it was actually completed and ready for field testing. (Note: When we suggest in the report that the vehicle has been ªcompletedº, keep in mind that this word is used rather loosely. Whenever you develop a prototype, it quickly becomes clear that there are always adjustments, revisions, and improvements that can be made, even when the prototype is fully operable. Some of the challenge of developing a prototype is then determining when it no longer requires investment of further resources. The best advice we could give to folks hoping to develop a new tool or a prototype is to start as early as you can, and as much as possible keep the construction phase from dragging out into the growing season. There is a period of time between learning that you have been awarded grant funding and the actual moment when you receive the funds where you may be unable to proceed, but if you have any cash on hand whatsoever it would be wise to accomplish as much as possible. 2.) Frame and Steering The frame itself is made from 0.065º thickness 1.5º square mild steel tubing, and 3 standard bicycle head tubes, headsets, and forks. Two of these sets allow the front forks/kingpins to rotate for steering. The other one allows the entire front end of the vehicle to pivot in a vertical plane around a forward pointing axis. This keeps all four wheels on the ground in undulating or bumpy terrain. To make this forward facing axis pivot, the fork blades were cut off the third fork and discarded. The top portion of the third fork was then welded to the front of the rear frame. This pivot is quite similar to how modern tractors keep all of their wheels in contact with the ground without suspension. The remainder of the suspension and necessary soil flotation was provided by large, 2.5º, 3º or 3.7º pneumatic bicycle tires. The fork head tubes were installed perpendicular to the pivot head tube, on another section of square tubing, but could have used 22-30 degrees of tilt back from the vertical to create a more proper amount of trail for the steering system. To get around this, we flipped the forks backward to move the steering axis to a more stable location, which created a caster action that reduced the need to steer the vehicle when riding it in wheel tracks. The steering system used three modified quill style bicycle stems to form an Ackermann style steering setup. One stem was modified to provide a post that provided a pivot for the central moving parts of the steering system. With that pivot in the center and attached to the headset that held the front end of the vehicle to the rear, we were able to isolate the rotation of the front end in the vertical plane from the work of steering. A rotating plate on the central pivot point took steering input from the steering lever attached to the main frame between the riders and transfered it around the pivot point to two tie rods that connected to the final two stems, each affixed to a fork and responsible for turning one of the front wheels. While the initial steering setup worked, we began to use it less and less in favor of turning the wheels by simply pushing their rims and tires. To achieve this, we kept the linkage between the central pivot and the two front wheels, and so moving one wheel also moved the other.

Load more